It took over three hours because there was a car accident and the street was blocked for two hours.

blocked 是动词 block 的过去分词形式，在句中表示被动。block 的基本意思是"阻挡、堵塞"，指用障碍物阻挡通行或视线。blocked 在这里表示"被堵塞、被封锁"的状态，指道路因事故而无法通行。